Six novel ATM mutations in Italian patients with classical ataxia-telangiectasia.

Mutations in the ATM gene are responsible for the autosomal recessive syndrome Ataxia Telangiectasia (AT). In a group of 26 classical AT Italian patients studied by protein truncation test (PTT), we identified six new mutations, never reported so far. Mutations -spread over the entire ATM coding sequence with not clear 'hot-spot'- are four frameshifts (2192_2193insA, 3110delC, 7150delA, 8368delA), one splice site alteration (8850G>T, causing exon 63 skipping) and one nonsense change (6913C>T, Q2305X). The identification of ATM gene mutations is important for understanding the molecular basis of the disease, and is essential for diagnosis and genetic counseling.